O

Figure 7.15 Some ecdysteroid examples. Makisterone A is used by some insects, including

Apis mellifera and Drosophila melanogaster, and by crabs and is a phytoecdysteroid in Podocarpus trees and the wildflower Lychnis flos-cuculi (ragged robin). Ecdysone 22-palmitate is an example of a storage product found in insect ovaries and eggs. Ajugasterone C is an example of a phytoecdysteroidfrom the Labiatae, Compositae and Verbenaceae, but also identified in an Anthozoa (corals and sea anemones)

kingdom, and many variations of the ecdysone structure have been identified. The number of phytoecdysteroids is now in the hundreds. They tend to be concentrated in the growing tips of plants and are presumed to act as anti-hormones, inducing premature moulting in the insects feeding on the plant (see The Ecdysone Handbook, edited by Harmatha, MarionPoll and Wilson, http://ecdybase.org). By a strange twist in the battle between plants, insects, and other predators. 22-acetyl-20-hydroxy-ecdysone has been found in high concentration in the defensive glands of the beetle Chrysolina carnifex.

Further sterols will be encountered among plant substances sequestered by insects (Chapter 10).